Jacklac asked a very good question: how many packs would you expect to have to buy to get all 4 stamps?
It's challenging to calculate because:
a) there are 1000 Orr signed sheets vs 500 for each of the other 3.
b) while the chances are 1 in 50 of getting a pack with an autograph, it's unlikely that you'll get 4 different signatures consecutively. That is, you may need to get 6 packs with an autograph before you have the 4 different autographs.
Very, very roughly, maybe you'd need to spend $4K to $5K.
ebay is a better way to go. I picked up one card for less than $50.